But his campaign was a relative success as Labour's vote increased by almost ten per cent, gaining them MPs instead of losing them.

Ms Phillips said Theresa May's failure to admit a mistake over the ‘dementia tax’ contributed to her appalling campaign.

Writing on the Guardian website the Labour MP said: ”I would be lying if I denied that I cannot wait to sit opposite the Tories and laugh at their massive arrogance and complacency, but we have to get our own house in order, too.

"If Labour reacts to the election result with its own complacency, we will look like a party happy to be in opposition.

“A little bit of mea culpa goes a long way, and the Labour party has a lot of humble-pie eating to do, too.

Jeremy Corbyn at his packed out pre-election rally in Birmingham (Image: Birmingham Mail)

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“We shall return to parliament this week; For those of us who always worried about Jeremy Corbyn’s electability, it is time to stand up and say that we got some of that wrong.”

Ms Phillips said Labour MPs who previously rejected Corbyn would go various ways, with some signing up to his bandwagon and others remaining critical - as Corbyn himself did during the New Labour era.

She added: “The group I will be in is the one that recognises that we didn’t win this election, but we are on the way to winning the next one if we get it right.

"I will never be a blinkered cheerleader of anyone (ask my kids), and while I got his electability half-wrong I would be doing him and the country a disservice by donning the white robes of worship and ignoring my concerns.”

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Ms Phillips said she had always retained open communications with the Labour leader - complaining about the ‘horrid vicious sexism’ of his supporters towards her at one time, while sharing campaign intelligence from Yardley doorsteps at others.

“I told him what I was hearing on the streets and what might and might not work. To this, he responds well,” she said.

And in a rallying call to colleagues across the House of Commons she added: “I have not always behaved well.

"I can admit that. I get things wrong, I learn.

"The most important thing for everybody to remember is that the hung parliament tells us we all got it wrong.

"So let’s be grown up enough to admit that, and then we can all just get on with sorting it out.”